1. Field of the Invention
This invention pertains to a jack assembly for use in the telecommunications or signal transmission industries. More particularly, this invention pertains to an improved switch assembly for such a jack.
2. Description of the Prior Art
Switching coax jack assemblies for use in the telecommunications or signal transmission industries are well known. An example of such is shown in commonly assigned U.S. Pat. No. 4,749,968 to Burroughs dated Jun. 7, 1988. The Burroughs patent teaches a switching coax jack having a housing which contains two parallel spaced apart internal conductors. Ports on the forward end of the jack permit a plug to be inserted within the jack housing to make electrical contact with the conductors. The Burroughs patent teaches two configurations where the forward end of the jack has either one or two forward ports.
In Burroughs, a switch assembly is provided for normally connecting the internal conductors but breaking the electrical connection upon insertion of a jack plug into either of the forward ports. With best reference to FIG. 11 of U.S. Pat. No. 4,749,968, the jack includes a switch assembly 156 having a normal spring 164 in a generally V-shaped configuration extending between the conductors 150,158. Upon insertion, a jack plug 52 engages a termination spring 168 which deflects to urge a first portion of a normal spring 164 away from conductor 150.
In switch designs, a risk of failure is presented by cyclic deformation of the normal spring by repeated insertion of a jack plug into the jack assembly. Namely, the deformation of the normal spring may result in breakage or plastic deformation of the normal spring.
The consequences of failure of the normal spring can best be appreciated by consideration of the environment in which a jack assembly is used. The jack assembly is one of several assemblies and other elements combined in a module (referred to as a "DSX module"). Examples of such modules are shown in U.S. Pat. No. 4,815,104 (FIGS. 1-6). In the event of failure of a normal spring in a jack assembly, the entire module must be replaced. This has severe economic consequences. The spring which fails is typically inexpensive (for example, less than $1.00 U.S.). On the other hand, the module which must be replaced upon failure of this spring can be quite expensive (typically greater than $200.00 U.S.).
Even more significant than the adverse economic consequences resulting from spring failure is the interruption in data or signal transmission resulting from such failure. Modules incorporating switching coax jacks are commonly used in the telecommunications industry for cross-connecting voice or data transmission lines. At high signal speed transmission rates (known in the industry as DS-3 rates or greater), a single DSX module may handle 672 voice conversations simultaneously. If a single normal spring fails within the DSX module, the module fails and the many customers being serviced by the module have their service interrupted.
Due to the significant economic and service interruption consequences attributable to spring failure, the telecommunications industry has prudently placed a high premium on reliability of spring contacts used in switching coax jacks. Accordingly, while designs such as that shown in the Burroughs patent are commercially satisfactory (i.e. the products are manufactured and designed to have a cycle life greater than any reasonably anticipated cycling in the field and, therefore, they very rarely, if ever, fail), the industry is continually looking for ways to increase the cycle life of such springs. Cycle life means the number of times that a spring may be alternately deformed and released before failure.
Customers continue to look for improved cycle life and may often make purchasing decisions based on improved cycle life. This is true even though prior device cycle life greatly exceeds anticipated cycling experienced in the field. Therefore, improvements in cycle life are of significant economic consequence.
It is an object of the present invention to provide a switching coax jack having an improved switch assembly to dramatically enhance the cycle life of springs within the jack.